Rapid detection and tracking of Omicron variant of SARS-CoV-2 using CRISPR-Cas12a-based assay.

BACKGROUND

The newly emerged SARS-CoV-2 variant of concern (VOC) Omicron is spreading quickly worldwide, which manifests an urgent need of simple and rapid assay to detect and diagnose Omicron infection and track its spread.

METHODS

To design allele-specific CRISPR RNAs (crRNAs) targeting the signature mutations in the spike protein of Omicron variant, and to develop a CRISPR-Cas12a-based assay to specifically detect Omicron variant.

RESULTS

Our system showed a low limit of detection of 2 copies per reaction for the plasmid DNA of Omicron variant, and could readily detect Omicron variant in 5 laboratory-confirmed clinical samples and distinguish them from 57 SARS-CoV-2 positive clinical samples (4 virus isolates and 53 oropharyngeal swab specimens) infected with wild-type (N = 8) and the variants of Alpha (N = 17), Beta (N = 17) and Delta (N = 15). The testing results could be measured by fluorescent detector or judged by naked eyes. In addition, no cross-reaction was observed when detecting 16 clinical samples infected with 9 common respiratory pathogens.

CONCLUSIONS

The rapid assay could be easily set up in laboratories already conducting SARS-CoV-2 nucleic acid amplification tests and implemented routinely in resource-limited settings to monitor and track the spread of Omicron variant.